The concept of making inexpensive microfluidic channels on paper and other woven and non-woven fibrous and porous surfaces to produce a microfluidic system been successfully proven. Paper in sheet form is readily obtainable and can produce a very low cost substrate for such a microfluidic system. One aim of building such systems has been to fabricate low-cost bio-analytical and indicator devices, with direct envisaged applications in detecting waterborne bacteria in drinking water, the presence of some specific protein or biomarkers in body fluid (cancer test), the level of glucose and other bio-chemical substances in human or animal blood and urine samples. Development of low-cost paper-based bio-analytical and environmental analytical devices have so far allowed quick and single step reaction to detect analytes in a fluid sample. Researchers in Harvard University led by Whitesides (see Martinez, A. W., Phillips, S. T., Butte, M. J. and Whitesides G. M., and “Platform for Inexpensive, Low-Volume, Portable Bioassays”, Angew. Chem. Int. Ed. 46, 1318-1320 (2007)) have recently created channels on paper by printing patterns of conventional photoresists polymers (PDMS). Paper provides the capillary channels, while the photoresist polymers form the barrier which defines the channel. More recently, the Harvard group used an x-y plotter to draw channels on paper surface (see Bruzewicz, D. A., Reches, M. and Whitesides, G. M., “Low-Cost Printing of Poly(dimethylsiloxane) Barriers to Define Microchannels in Paper, Anal Chem. 80, 3387-3392 (2008) and Martinez, A. W.; Phillips, S. T.; Carrilho, E.; Thomas III, S. W.; Sindi, H.; Whitesides, G. M., “Simple telemedicine for developing regions: camera phones and paper-based microfluidic devices for real-time, off-site diagnosis”. Anal. Chem. 80 (2008) 3699-3707)). The plotter's pens were filled with a hydrophobic solution of polydimethyl siloxane (PDMS) in hexane, and a plethora of patterns 10 cm long with channel 1 cm to 2 mm wide were created. Their second micro-channels system created on paper surface overcame a major drawback of the first one, ie the rigid and brittle barrier material of conventional photoresist polymers. Their second system, however, has a poor channel resolution and definition, since the penetration of PDMS solution in paper sheet cannot be controlled.
In U.S. Pat. No. 7,125,639, Molecular Transfer lithography, the inventor Charles Daniel Schaper (class 430/253, 430/258) describes a process for patterning a substrate comprising the steps of: 1) coating a carrier with a photosensitive material, 2) exposing the photosensitive material to a pattern of radiation, and 3) physically transferring the exposed material to the substrate.
In U.S. Pat. No. 6,518,168, Self-assembled monolayers direct patterning of surfaces, by Paul G Clem et al (filing date Nov. 2, 1998), A technique for creating patterns of material deposited on a surface involves forming a self-assembled monolayer in a pattern on the surface and depositing, via chemical vapor deposition or via sol-gel processing, a material on the surface in a pattern complementary to the self-assembled monolayer pattern. The material can be a metal, metal oxide, or the like.
In WO/2008/060449 MICROFLUIDIC DETECTOR, by BUTTE, Manish, J. et al (Application date Nov. 9, 2007), Articles and methods for determining an analyte indicative of a disease condition are provided. In some embodiments, articles and methods described herein can be used for determining a presence, qualitatively or quantitatively, of a component, such as a particular type of cell, in a fluid sample. In one particular embodiment, a low-cost microfluidic system for rapid detection of T cells is provided. The microfluidic system may use immobilized antibodies and adhesion molecules in a channel to capture T cells from a fluid sample such as a small volume of blood. The captured T cells may be labelled with a metal colloid (eg, gold nanoparticles) using an antibody specific for the T Cell Receptor (TCR), and metallic silver can be catalytically precipitated onto the cells. The number of T cells captured can be counted and may indicate a disease condition of a patient such as severe combined immune deficiency or human immunodeficiency virus.
None of the above noted patents describe any functional components for controlling the movement of fluids or otherwise influencing the fluid within the microfluidic system. Furthermore, multiple-step reactions cannot be performed by the above described systems.
It is therefore an object of the present invention to provide a microfluidic system incorporating such functional components.
It is another preferred object to provide a microfluidic system allowing multiple-step reactions or functions to be performed.